Traffic simulation

References

1. ^ abFrom the road found beside the zone, TryDrive walks up to 30 steps (MAXDIS), each step trying the four directions in turn from a random one and never straight back. The trip succeeds once the current tile borders a destination: tiles 423–816 (commercial zones through the nuclear plant) for a residential trip, 249–698 (houses through the seaport) for a commercial one, and 249–423 (houses to the first commercial tile) for an industrial one.CodeMicropolis (SimHacker/micropolis)
   How we know

   68#define MAXDIS 30
   

   207  for (z = 0; z < MAXDIS; z++) {	/* Maximum distance to try */
   

   235    if (realdir == LDir) continue;	/* skip last direction */
   

   278  static short TARGH[3] = {NUCLEAR, PORT, COMBASE};	/* for destinations */
   

   356#define COMBASE		423
   

   Checked against the evidence by its author, an AI model, 2026-10-21.

   Checked by a second AI model, 2026-10-21.

   In the claim ledger

2. ^ abAt a dead end TryDrive drops its last saved position and adds 3 to the step count, but it doesn't move back: the next try starts from the same tile, still barred from the way it came, so it fails again until the steps or the saved positions run out, and the trip fails.CodeMicropolis (SimHacker/micropolis)
   How we know

   213	PosStackN--;
   

   236    if (RoadTest(GetFromMap(realdir))) {
   

   Checked against the evidence by its author, an AI model, 2026-10-21.

   Checked by a second AI model, 2026-10-21.

   In the claim ledger

3. ^When the simulation visits a zone, a residential zone tries a trip if its population exceeds a random 0–35, a commercial or industrial zone if its population exceeds a random 0–5. If none of the 12 tiles bordering its 3×3 footprint (corners excluded) is a road or rail tile, the trip fails at once and the zone declines.CodeMicropolis (SimHacker/micropolis)
   How we know

   239  if (tpop > Rand(35)) TrfGood = MakeTraf(0);
   

   200  if (tpop > Rand(5)) TrfGood = MakeTraf(1);
   

   169  if (tpop > Rand(5)) TrfGood = MakeTraf(2);
   

   104  else return (-1);		/* no road found */
   

   162  static short PerimX[12] = {-1, 0, 1, 2, 2, 2, 1, 0,-1,-2,-2,-2};
   

   1199  range++;
   

   Checked against the evidence by its author, an AI model, 2026-10-21.

   Checked by a second AI model, 2026-10-21.

   In the claim ledger

4. ^A successful trip adds 50 to the traffic density of the 2×2 block under every second road tile on its path (rail tiles aren't counted). A sum above 240 is set to 240 one time in six, which also sends the helicopter there; otherwise it's stored in a byte, so a sum above 255 wraps around to 0–49. Each cycle, density above 200 falls by 34, density from 25 to 200 by 24, and density of 24 or less drops to 0.CodeMicropolis (SimHacker/micropolis)
   How we know

   239      if (z & 1)			/* save pos every other move */
   

   134	TrfDensity[SMapX >>1][SMapY >>1] = z;
   

   475extern Byte *TrfDensity[HWLDX];
   

   470  if (z = Oframe[COP]) DrawCopter(view, z);
   

   264	  if (z > 200) TrfDensity[x][y] = z - 34;
   

   Checked against the evidence by its author, an AI model, 2026-10-21.

   Checked by a second AI model, 2026-10-21.

   In the claim ledger